The goal of this research is to develop the necessary technologies of MR microscopy using hyperpolarized He-3 and Xe-129 to enable in vivo imaging of the lungs of animals under environmental stress. In vivo three dimensional (3-D) H-1 images will be used to measure changes in the airways down to terminal bronchioles. Hyperpolarized gas imaging will be used to produce ventilation movies with 1 mm3 resolution with 100 msec time frames. The elastase model of emphysema will be used to test the sensitivity and specificity of MR microscopy and hyperpolarized gas imaging. The developed imaging tools will be applied to the same model where animals are to undergo exposure to increased particulates. The results will provide the environmental toxicologists with extraordinary new methods to follow progression and regression of the effects of toxic exposure with increased biostatistical accuracy and lower cost due to smaller animal populations that would be required.